<!--
    1.24基础上将固定宽度200px换成百分比30%
    2.wrapper margin-right:-30%为navigation、extra留出空间 width:100%不能省
    3.content margin-right:30%
    4.navigation 宽度30%，位于content左侧 float:left
    5.extra 宽度30%，位于content左侧 float:left clear: left
-->
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        #header, #footer{
            height: 50px;
            background-color: gray;
            clear: both;
        }
        #wrapper{
            margin-right: -30%;
            float: right;
            width: 100%;
        }
        #content{
            margin-right: 30%;
            height: 100px;
            background-color: gold;
        }
        #navigation, #extra{
            float: right;
            height: 50px;
            width: 30%;
        }
        #navigation{
            background-color: fuchsia;
        }
        #extra{
            background-color: forestgreen;
        }
    </style>
</head>
<body>
    <div id="container">
        <div id="header">Header</div>
        <div id="wrapper">
            <div id="content">Content</div>
        </div>
        <div id="navigation">Navigation</div>
        <div id="extra">Extra stuff</div>
        <div id="footer">Footer</div>
    </div>    
</body>
</html>